Supplemental Braking Assist

In addition to preventing wheel lock up during braking events, the Anti-Lock Brake System (ABS) module is also able to provide supplemental hydraulic brake assist through the use of the hydraulic pump motor and the Hydraulic Control Unit (HCU). This is done in the event of a severe vacuum loss at the brake booster, to maintain the distance gap set by the adaptive cruise control system or to aid in the avoidance of forward collisions.

The Anti-Lock Brake System (ABS) module utilizes the Hydraulic Control Unit (HCU) and hydraulic pump motor to aid in bringing the vehicle to a safe, controlled stop in the event of severe vacuum loss at the brake booster. The Anti-Lock Brake System (ABS) module continually monitors the vacuum in the brake booster through the use of a vacuum sensor. When the vacuum sensor indicates vacuum is below a predetermined level, a Diagnostic Trouble Code (DTC) is set in the Anti-Lock Brake System (ABS) module. If this occurs during a braking event or if the driver attempts to stop the vehicle with a low vacuum condition in the brake booster, the Anti-Lock Brake System (ABS) module activates the hydraulic pump motor in the Hydraulic Control Unit (HCU) to assist with vehicle braking.

On vehicles equipped with adaptive cruise control, the Cruise-Control Module (C-CM) monitors the area forward of the vehicle. When an object enters this area and closes the distance gap set by the driver, the Cruise-Control Module (C-CM) sends a deceleration request to the Anti-Lock Brake System (ABS) module over the High Speed Controller Area Network (HS-CAN) (either an adaptive cruise control deceleration request or a collision avoidance deceleration request). When the deceleration request message is received, the Anti-Lock Brake System (ABS) module activates the hydraulic pump motor and solenoid valves in the Hydraulic Control Unit (HCU) to slow the vehicle down to maintain the distance gap set by the driver. Once the distance gap set by the driver is achieved, the Cruise-Control Module (C-CM) stops sending the deceleration request message and the Anti-Lock Brake System (ABS) module deactivates the hydraulic pump motor and solenoid valves in the Hydraulic Control Unit (HCU). If the Cruise-Control Module (C-CM) determines that the amount of braking provided by the Anti-Lock Brake System (ABS) module is insufficient, the Cruise-Control Module (C-CM) sends a forward collision avoidance braking request message to the Anti-Lock Brake System (ABS) module and warns the driver, both audibly and visually, through the use of the Head Up Display (HUD). After receiving the braking request message, the Anti-Lock Brake System (ABS) module waits for brake pedal input and at that time applies maximum braking assist using the hydraulic pump motor and the Hydraulic Control Unit (HCU). For additional information on the adaptive cruise control system, REFER to ADAPTIVE CRUISE CONTROL (ACC) OPERATION . For additional information on the collision avoidance system, REFER to COLLISION AVOIDANCE OPERATION .